Circular  No.  109. 


■ 


United  States  Department  oi  Agriculture, 


BUREAU    OF    ENTOMOLOGY. 
L.  O.  HOWARD,  Entomologist  and  Chief  of  Bureau. 


THE  LEOPARD  MOTH. 

:>  rn  pyrina  Fab.  Ia 
By  I..  0.  Howabd  and  1'   11.  •  'mittkm>i.s 
LNTBOD1  <   rOBT. 

Deciduous  trees  of  many  kinds,  grown  for  shade  and  for  ornament 
in  northern  New  Jersey  and  eastern  NCw  York,  arc  subject  to  severe 
injury  by  the  larval  stage  of  the  European  leopard  moth  (Zeuzera 
pyrina  Fab.).  Among  the  shade  trees,  elms  and  maples  suffer  the 
tot  damage,  but  as  this  species  is  a  very  general  feeder  it  attacks 
practically  all  descriptions  of  trees  and  shrubs  with  the  except  ion  of  the 
evergreens.  In  the  region  mentioned  this  species  is.  everything  con- 
sidered, the  most  serious  menace  to  the  growth  of  shade  trees,  since, 
unlike  the  majority  of  lepidopterous  insects,  the  larva1  of  the  leopard 
moth  do  not  feed  upon  the  foliage,  hut  bore  into  the  branches  of  the 
plants  which  they  infest  and  feed  upon  the  living  wood.  The  larva- 
usually  begin  operations  in  twigs  and  small  branches  and  with  their 
larger  growth  bore  and  tunnel  into  the  larger  branches  and  trunks. 
This  work  has  the  effect  of  girdling,  the  injured  portion-  being  blown 
down  by  heavy  wind  storm-,  while  in  the  case  of  severe  attack  the 

u th  of  the  tree  is  checked,  frequently  causing  it-  death.     Attack  is 
not  confined  solely  to  shade  and  ornamental  plant-,  but  orchard-  are 
n  injured. 

DX84  i: i  !•  i  i \  i 

Injury  by  this  species  i>  accomplished  solely  by  the  larva,  which  is 
a  fleshy,  grublike  caterpillar,  pale  yellowish  in  color,  frequently  with 

pinkish  tinge.  The  head,  thorax,  and  anal  plates  are  brownish- 
black  and  the  surface  of  the  body  i>  very  Bparsely  hairy  hut  covered 


1  Family  <  -\  nonym- 

09 


with  large  and  prominent  tubercles  arranged  as  shown  in  the 
illustration  (fig.  1,  c).  When  fully  mature  the  larva  attains  a  total 
length  of  about  2  inches.  A  lateral  view  of  the  larva  in  its  burrow 
is  shown  in  figure  1  at  c. 

This  species  derives  its  name  from  the  spotted  appearance  of  the 
moth,  illustrated  at  figure  1,  a,  b.  There  is  great  diversity  in  the 
size  of  the  two  sexes,  the  female  (a),  which  is  a  heavy-bodied  moth 
and  a  very  feeble  flyer,  being  much  the  larger.  It  will  be  noticed  that 
the  smaller  male  (b)  has  a  more  slender  body,  which  permits  a  more 
ready  flight,  and  is  also  distinguished  from  the  female  by  the  pos- 


Brail"  'II:      MINI 

wV  v  BBS  !  I  \  sn  i* t<l" 


Fig.  1.— The  leopard  moth  (Zcuzcra  pyrina):  a.  Adult  female;  b,  adult  male;  c,  larva;  d, empty  pupal 

case.    Enlarged.     (Original.) 

session  of  broad  bipectinate  or  feathery  antennae.  The  wings  are 
semitransparent  and  white,  thickly  dotted  with  blackish  spots 
which  are  more  or  less  distinctly  tinged,  giving  them  a  dark  blue  or 
greenish  cast.  The  thorax  is  marked  with  six  large  black  spots  and 
one  small  one,  the  latter  being  located  in  the  center.  The  female  has 
a  wing  expanse  of  upwards  of  one  and  a  half  inches,  while  that  of  the 
male  is  much  less. 

An  empty  pupa-case  in  its  cell  in  the  wood  is  shown  in  the  illustra- 
tion at  d. 

[Cir.  109] 


ORIGIN  M     Hi  'Ml      \\i>    DISTRIB1   I  i"\. 

The  leopard  moth,  like  bo  man]  other  dangerous  pests,  is  a  European 
species  which  has  been  introduced  into  the  United  States  in  com- 
paratively  recent  years.      Its  old  world  distribution   is  credited 
central  and  southern  Europe,  southern  Sweden,  southwestern  Africa, 
Algeria,  and  northern  Morocco,  and  tin-  western  portion  of  Asia  Minor. 

This  Bpecies  was  introduced  into  the  United  States  Borne  time 
prior  to  1879,  in  which  year,  on  the  authority  of  Mr.  Jacob  Dull,  a 
living  moth  was  captured  in  a  spider's  web  al  Hoboken,  N.  -I."  In 
lsM  Dr.  E,  B.  Southwick,  then  entomologist  of  the  public  park-  of 
Nrw  York  City,  recognized  the  destructive  work  of  this  species  in 
Centra]  Park.*  In  1887  it  was  Been  al  Newark,  N.  J.,  but  was  nol 
actually  recorded  as  occurring  in  this  country  until  the  following 
\ ear.  In  1890  the  junior  author  observed  the  moths  at  electric  lights 
at  ( Grange,  X.  J. 

Fortunately  the  spread  of  this  insect,  part  icularly  in  the  immediate 
vicinity  of  New  York  City,  has  been  very  slow,  a  fact  which  may  be 
attributed  to  several  causes,  (1)  the  slowness  of  the  flight  of  the 
female,  (2)  the  dominance  of  sparrows  in  large  cities,  causing  our 
native  bird-,  such  as  woodpeckers,  to  be  driven  to  the  country,  where 
the\  destroy  the  moths,  and  (3)  the  bowl-shaped  electric-light  globes, 
hollow  at  the  top  and  closed  at  the  bottom,  which  were  formerly  in 
general  use  in  our  large  cities.  The  males  are  Btrongly  attracted  to 
brilliant  lights  and  many  were  captured  and  perished  in  these  globes 
in  earlier  years.  Other  cities  in  New  Jersey  where  this  species  has 
been  troublesome  are  Elizabeth,  [rvington,  Montclair,  Arlington, 
Asbury  Park,  Ocean  Grove,  and  New  Brunswick.  Mr.  II.  M.  Russell 
of  this  Bureau  collected  specimens  at  Bridgeport,  Conn.,  in  1901. 
The  species  is  now  an  inhabitant  also  of  Staten  Island  and  has  spread 
on  Long  Island  well  beyond  the  confines  of  greater  New  Y'ork.  South- 
ward it   was  reported  a  pest,  in   1901,  at  Ocean  (dove.   N.  .1..  and  by 

1905  it  was  recorded  by  Kelt  as  occurring  at  rlensico,  N.  Y..  25  miles 
north  of  New  York  City.  By  1907  it  was  captured  at  New  Haven, 
Conn.,  by  Prof.  II.  W.  Foote.  It  i-  now  stated  to  he  injurious  in  the 
vicinity  of  Boston,  Ma—. 

i  ood  i'i  a\  re. 

In  it-  original  home  the  leopard  moth  is  recorded  a-  living  on  a 
considerable  number  of  common  tree-,  including  elm.  lime  or  linden, 
ash,  beech,  birch,  walnut,  oak.  chestnut,  poplar,  alder,  and,  rarely, 
horse-chestnut.  Among  orchard  tree-  it  is  reported  to  do  injury  to 
pear,  apple,  and  plum.     In  the  United  State-  it  attacks  all  of  these 

<j  Entomological  Neva,  March,  1904.  p.  no.  b  Insert  Life,  Vol.  VII,  p.  138. 

[Or.  109] 


trees  and  many  others,  the  list  including  such  important  shade  trees 
as  have  been  mentioned,  as  also  practically  all  of  the  maples,  elms, 
and  oaks,  mountain  ash,  tulip  tree  (Liriodendron  tulipifera),  aspen, 
the  willows,  and  such  shrubs  as  privet,  lilac,  and  honeysuckle.  A 
list  of  trees  which  this  species  has  been  actually  observed  to  attack 
was  compiled  in  1894  by  Doctor  Southwick  and  includes  77,  observed 
in  the  public  parks  of  Xew  York  City  alone.  A  total  list  of  83  trees 
and  shrubs  was  made  at  that  time." 

It  will  be  seen  by  the  list  of  food  plants  already  presented  that 
the  number  could  be  almost  indefinitely  extended,  particularly  in 
reservations  like  Central  Park,  New  York  City,  and  Prospect  Park, 
in  Brooklyn,  where  special  effort  has  been  made  to  bring  together  a 

great  variety  of  trees  and  shrubs.  The  in- 
sect is,  in  fact,  nearly  omnivorous,  attack- 
ing, as  previously  stated,  practically  all 
forms  of  woody  plants  which  are  of  suitable 
size  for  its  purpose,  with  the  exception  of 
conifers. 

HABITS    AND    LIFE    HISTORY. 

In  Germany  the  moths  are  stated  to 
make  their  appearance  during  July  and 
August,  while  in  this  country  they  appear 
as  early  as  May  and  continue  issuing  until 
late  in  September. 

The  gravid  female,  being  particularly 
heavy,  is  unable  to  fly  very  far  or  very 
high.  She  deposits  her  oval,  salmon-col- 
ored eggs  in  a  large  mass  or  group,  when 
not  in  confinement,  and  as  many  as  300 
eggs  have  been  counted  in  a  single  mass. 
This  is,  however,  probably  not  the  maxi- 
mum number,  since  an  estimate  of  as  many 
as  1,000  has  been  made.  The  eggs  are  in- 
troduced by  the  rather  hard  ovipositor  into  the  soft  tissue  of  young 
growth  where  the  bark  is  smooth,  or  are  inserted  into  crevices  in  the 
rough  bark  of  older  trees. 

The  larva?  soon  hatch — hi  about  ten  days,  according  to  Mr.  J. 
V.  D.  Walker — and  penetrate  the  wood,  frequently  entering  the 
nearest  crotch  but  boring  in  at  other  points,  and  burrow  tunnels  into 
the  heart  or  pith  of  twigs  and  the  heartwood  of  the  larger  branches 
or  trunks.  "When  a  larva  has  grown  too  large  for  the  branch  in  which 
it  is  feeding  it  crawls  out  and  migrates  to  a  larger  one.     In  a  single 

"See  list  on  page  529,  Rep.  Ent.  N.  J.  Agr.  Exp.  Sta.  for  1894.     This  article,  by 
Dr.  J.  B.  Smith,  covers  pages  517-533  and  presents  a  very  complete  account  of  the  insect. 
[Cir.  109] 


Fig.  2. — Section  of  wood  showing  bur- 
row and  girdling  effect  produced  by 
larva  of  leopard  moth.  Reduced. 
(From  Insect  Life.) 


tree  6  inches  in  diameter  Southwick  observed  as  many  us  -ix  larva\ 
an \  <>nc  of  which  would  have  been  able  to  destroy  the  tree  if  no!  re- 
moved. Mi.  A.  Iliit'ii.il  wrote  that  in  maple  trees  which  this  spe* 
was  infesting  at  Ocean  Grove,  N  J.,  there  was  an  average  of  from 
-ix  to  eight  borers  to  a  tree  and  thai  he  had  found  from  ten  t<»  1  i f t •  •« -i i . 
and  in  one  instance  as  high  as  thirty  four,  in  a  single  tree.  I>>  the 
time  tlic  larvae  within  have  attained  full  growth  infested  limbs  of  a 
certain  size  arc  likely  to  break  off,  especially  during  or  after  a  Bevere 
atorm,  for  the  full-grown  larva  in  man]  girdles  the  branch. 

The  manner  of  girdling  is  shown  at  the  top  of  the  Bection  of  wood 
illustrated  in  figure  _'.  In  1893,  after  everj  Btorm  in  Central  Park 
greal  quantities  of  limbs  were  Been,  some  entirely  broken  off  and 
others  still  hanging  to  the,  trees. 

'The  larva,  when  fully  mature,  transforms  to  pupa  within  the 
burrow,  the  change  beginning  to  occur  during  the  second  May  after 
the  hatching  of  the  eggs,  the  larva  thus  requiring  nearly  two  years 
to  complete  its  growth.  The  pupa.  I>\  means  of  a  sharp  protuber- 
ance on  it-  head,  i-  enabled  to  force  it-  way  partly  OUl  of  the  burrow  . 

after  which  the  skin  splits  open  and  the  moth  emerges.  Theemptj 
pupal  skin  remains  for  some  time  projecting  From  the  orifice. 

The  presence  of  this  borer  in  a  branch  is  manifested  by  little 
accumulation-  of  chip-,  matted  excrement,  or  fra--.  which  indicate 
the  entrance  to  the  burrow-.  After  a  time  these  orifice-  are  closed 
from  within  b)  a  silken  web,  which  i-  doubtless  to  protect  the  con- 
tained insect  from  it-  natural  enemies.  Smaller  twigs  wilt  and 
break  oil'  and  often  it  is  onl\  when  the  severed  twigs  or  branches 
have  been  broughl  down  in  number-  by  high  winds  that  the  work 
of  the  insect  is  first  recognized.  Where  the  larger  larvae  have 
worked  just  under  the  bark  this  -plit-  open  the  next  season,  leaving 
an  uglj  -car  a-  a  reminder  of  it-  pernicious  operations. 

\  \  11  i:  vi.  i  nil  k-. 

\"  specific  natural  enemies  of  the  leopard  moth  appear  to  have 
been  recorded  in  this  country,  although  in  Europe  E.  A.  Fitch  has 
reared  an  indeterminate  chalcidid  of  the  .-uhfamih    EncyrtUMB. 

In  the  explanation  of  the  cause  of  the  -low  spread  of  the  moth 
from  cities  and  large  town-  to  the  country,  allusion  ha-  been  made 
to  the  fact  that  native  bird-  probably  assist  in  holding  this  insect 
in  check  in  the  suburbs.  Actual  observations  on  this  head  appear 
to  be  wanting,  but  there  are  the  best  of  reasons  for  believing  that 
birds,  like  the  woodpeckers,  which  naturally  look  over  the  bark 
and  collect  all  kinds  of  borer.-,  prey  on  this  species,  while  it  i-  believed 

o  Entom.  Mo.  Mag.,  Vol.  XVIII.  p.  116      Perha]  Dalm., 

mentioned  by  Dalla Torre  (not  M  -  Bymenoptei  >rum,  p.  .'it;. 

[Cir.  109] 


that  sparrows  sometimes  destroy  the  eggs  or  young  larvae  in  such 
places.  Smith  has  expressed  the  belief  that  when  the  insect  suc- 
ceeds in  getting  away  from  the  outskirts  of  cities  its  enemies  increase 
in  number,  many  insectivorous  birds  aiding  in  holding  it  down. 
During  the  da}"  the  moths  must  be  fed  upon  by  birds  and  later 
by  bats  and  night-flying  birds.  The  habit  of  the  larvae  of  desert- 
ing one  twig  and  migrating  to  a  larger  one  undoubtedly  leaves  them 
exposed  to  the  same  natural  enemies,  as  this  has  been  observed  to 
happen  in  the  daytime  as  well  as  after  nightfall.  It  follows  that  the 
protection  of  native  birds,  especially  the  woodpeckers  and  related 
species,  will  greatly  assist  in  restraining  the  undue  increase  of  this 
borer. 

METHODS    OF    CONTROL. 

The  protected  and  concealed  manner  of  life  of  this  species,  as 
shown  by  the  life  history,  which  will  apply  in  the  main  to  other 
borers  also,  renders  it  very  difficult  of  treatment  by  means  of  insect- 
icides or  other  direct  measures.  The  most  efficacious  remedial  meas- 
ure consists  in  cutting  off  and  destroying  affected  branches  and 
in  the  injection  of  bisulphid  of  carbon  into  the  holes  or  burrows 
where  the  larva?  are  at  work. 

Pruning  and  cutting  back. — Twigs  or  branches  which,  by  their 
wilting  or  by  the  frass  which  accumulates  at  the  entrance  to  their 
burrows,  indicate  the  presence  of  this  borer,  should  be  carefully 
searched  out,  the  smaller  ones  pruned  away  and  the  larger  ones 
cut  back,  the  amputated  portions  being  promptly  burned.  After 
windstorms,  the  affected  branches  which  have  fallen  to  the  ground 
and  those  which  remain  attached  to  the  tree  should  be  collected  and 
burned.  Wherever  trees  show  that  they  are  past  recovery  it  is  best 
to  take  them  out  and  promptly  destroy  them.  The  word  promptly 
is  used  advisedly,  for  this  insect,  as  has  been  shown  previously,  fre- 
quently migrates  from  one  twig  or  branch  to  another. 

Bisulphid  of  carbon. — In  the  case  of  young  and  rare  trees  and 
others  which  show  only  a  few  larval  burrows  in  the  bark,  bisulphid 
of  carbon  is  the  best  remedy  and  one  which  has  been  in  general  use 
against  the  present  species  in  the  public  parks  of  New  York  City.  It 
is  injected  into  the  openings  of  the  burrows,  and  the  openings  are 
afterwards  closed  with  various  substances.  For  this  injection  a 
mechanic's  long-spouted  oil  can  of  small  size  may  be  used  on  large 
trees,  but  against  a  related  species  the  writers  have  made  very  good 
use  of  a  small  glass  syringe,  such  as  may  be  purchased  at  any  drug 
store  for  ten  cents.  These  glass  svringes  are  most  serviceable,  be- 
cause the  exact  amount  of  bisulphid  may  be  seen  when  drawn  into 
the  syringe  and  because  the  reagent  does  not  injure  the  thread  pack- 

[Cir.  109] 


ing.°  Metal  syringes  may  also  be  used,  but  it  is  inure  difficult  to 
measure  the  exact  amount  and  the  bisulphid  acts  on  the  leather 
packing.  Rubber  syringes  can  not  be  used  because  of  rapid  corrosion. 
A I  >■  >u  i   a  teaspoonfuJ  of  the  liquid  bisulphid  is  sufficient   for  each 

Imiit"\\  . 

For  stopping  the  holes  after  injecting  the  liquid,  putty  and  moist 
clay,  advised  l>\  some,  have  oot  been  found  bo  serviceable  as  grafting 
wax.  Coal  tar  may  be  substituted  For  the  latter,  or  the  holes  maj  be 
closed  l>\  inserting  a  wooden  plug  and  breaking  '>r  sawing  it  off  level 
with  the  trunk.  In  anj  case  the  stopper  should  l>e  tight,  to  exclude 
water  from  rains,  which  might  tend  to  produce  decomposition  of  the 
surrounding  wood  or  in\  ite  other  insects,  like  black  ants  and  second- 
ary borers,  of  which  there  are  manj  species,  and  injurious  fungi. 

Carbon  bisulphid  should  be  handled  with  the  usual  precautions 
against  fire,  which  means  that  the  operator  should  not  smoke  while 
at  work.  Although  a  deadl)  poison,  it  will  Dot  injure  ordinarj 
tree-  when  applied  as  described. 

Killing  with  wires.  It  is  possible  t<>  reach  and  destroy  some  larve 
by  forcing  a  copper  or  other  pliable  w ire  into  the  channels.  This  is  a 
well-known  borer  remedy.  It  is  impossible,  however,  1>\  this  means 
to  kill  the  insects  in  all  cases,  owing  t<»  the  length  or  crookedness  "t 
the  harrows.     Bisulphid  of  carbon  should  then  he  used. 

Electric  lights.  'To  what  extent  electric  lights  arc  serviceable  a-  an 
agency  in  the  destruction  of  the  moths  of  this  borer  has  not  been 
definitely  determined.  Col.  Nicholas  Pike  and  Dr.  J.  B.  Smith, 
however,  have  advised  placing  shallow  pans  around  electric-light 
poles  in  and  around  parks  to  attract  the  moths.  The  pans  are  par- 
tially filled  with  water  and  a  few  drops  of  kerosene  are  poured  into 
them.  The  moths  flying  against  the  <j;lol>e>  drop  into  the  pans  and 
are  promptly  killed  when  they  come  into  contact  with  the  oil.  In 
this  way  many  males  can  he  destroyed. 

Inspection.  -In  large  parks  the  destruction  wrought  by  this  l><>rcr 
annually  is  an  important  item,  and  it  will  he  found  a  source  of  profit 
to  establish  a  system  of  inspection  consisting  in  the  employment  of 
parkkeepers  and    hoys,  and  others  who  may  he  engaged  at   lower 

»  During  the  la-t  years  >i  the  nineteenth  century  a  long  row  of  beautiful  red  oaks 
bordering  the  streel  between  the  grounds  of  the  Depart  meat  of  Agriculture  and  those 
of  the  Smithsonian  Institution  were  badly  infested  by  the  related  carpenter  worm 
{Prionoxythu  robinia  Pont.  |.     Nearly  every  tree  was  infested  and  frequently  two  or 

three  burrows  showed  near  the  (ops  of  the  trunks.      Bisulphid  of  carbon  was  applied, 
as  described  above,  and  the  hobs  closed  with  grafting  wax       A  year  later  no  in- 
could  be  found  at  work,   but   wherever  this  remedy  had  been  applied  a  small 
remained.     Two  years  later  these  had  entirely  disappeared  and  the  trees  looked  as  if 
they  had  never  been  infested. 

[Clr.  109] 


UNIVERSITY  OF  FLORIDA 


8 

3  1262  09216  5439 

wages,  to  keep  a  constant  lookout  for  evidences  of  borer  attack  on 
valuable  trees.  On  this  head  Southwick  has  reported  that  in  1893 
he  spent  two  months  in  fighting  this  insect  alone  in  the  city  parks  of 
New  York,  collecting  wagon  loads  of  limbs  and  branches  and  destro)7- 
ing  the  larvae  or  pupae. 

Maintaining  trees  in  thrifty  condition. — If  valuable  trees  are  to  be 
protected,  the  insect  should  not  be  allowed  to  breed  in  useless  growth. 
The  borers  in  such  trees  should  be  destroyed  or  the  trees  promptly 
felled  and  burned.  Care  should  be  exercised  in  transplanting  new 
trees,  and  fertilizers  should  be  used  in  order  that  the  trees  may  be 
always  thrifty,  the  better  to  withstand  attack.  This  means  protect- 
ing them  from  the  attack  of  aphides,  scales,  and  defoliators,  such  as 
tussock  moths  and  the  fall  webworm,  and  keeping  them  free  from 
disease. 

Finally,  in  the  control  of  this  species  promptness  and  thoroughness 
can  not  be  too  strongly  emphasized.  The  bisulphid  of  carbon 
remedy  should  always  be  used  where  applicable,  and  the  inspection 
system  advised  should  be  instituted  in  all  public  parks  and  on  city 
streets  infested  by  this  pest.  Individual  owners  of  valuable  trees 
should  become  acquainted  with  the  pernicious  nature  of  this  borer, 
and  united  action  should  be  secured  with  neighbors  who  also  suffer 
from  the  ravages  of  the  pest. 

Note. — After  this  publication  was  in  type  we  received  information  that  trees  in 
the  college  yard  of  Harvard  University,  Cambridge,  Mass.,  are  being  severely  injured, 
the  large  elms  being  the  most  seriously  attacked. 

Approved : 

James  Wilson, 

Secretary  of  Agriculture. 
Washington,  D.  C,  May  27,  1909. 

[CIr.  109] 

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